She is a member of the Caulfield Carnegie cycling club. She lives in Girona, Spain, with her husband, Greg Henderson, and their daughter.
She won the pursuit at the 2005 world championship, the 2005 World Cup and the 2006 Commonwealth Games in Melbourne. At the Cycling at the 2004 Summer Olympics Mactier broke the world record in the heats in the pursuit, but Sarah Ulmer set a new record in the final, relegating her to a silver medal.
In 2001 Mactier won in the national road championship. In 2002/2003 she was the Australian pursuit champion, and second in the 2003 world pursuit championship. She was 2003 and 2005 Australian Female Track Cyclist of the Year.